Smart power grids require large quantities of current and voltage metering sensors to track power flows, to get a voltage proportional to the one being measured, and take intelligent actions.
Known approaches to metering sensors in MV switchgear include using traditional magnetic core Voltage Transformers (VTs) which use electromagnetic induction but suffer from high weight, expense, and large space requirements and are limited in the voltage they can read because of the saturation of their ferromagnetic core.
Resistive divider technology can also be used but suffers from measurement accuracy concerns at higher voltages due to e.g. Johnson-Nyquist noise, thermocouple effects, and susceptibility to parasitic capacitances.
Capacitive voltage transformers exist and are commonly used in Medium and High voltage as voltage presence indicators or for voltage metering. However, the known transformers for metering MV are large, e.g. several meters high, and expensive. Further, known capacitive voltage dividers may have accuracy problems due to the variation of capacitance values caused by changes in ambient conditions such as temperature and humidity. Capacitive voltage transformers for voltage presence indication, such as U.S. Pat. No. 8,395,397 to Handshoe et al., are small but possess little accuracy. They generally serve merely to light up an LED that indicates voltage presence.
Therefore, there is a desire for a compact, accurate, capacitive voltage divider based metering sensor for MV and HV applications.